Hi! I make purses (over molds). Interior is Premo gold and 35-40% ultra light. On a second bake I put on a thin skin ( #7 Dream machine). With the difficulty of finding clay just now, I bought Kato for the outer layer. Will curing a Kato layer on top of cured Premo and ultra light burn the the already cured layer? Elizabeth from Louisville, KY

Hi Elizabeth,

I understand your concern. The recommended curing temperature for Premo and UltraLight is 275°F/135°C and Kato’s is 300°F/150°C. It is best, of course, to stick with what the manufacturers have recommended. But as with your situation, this isn’t always possible. What to do?

Have a look at the article here that talks a bit about mixing clay brands. It gives a bit of insight and what to do in other mixed-brand scenarios.

But in your specific situation, I see no problem with baking the project at 300°F/150°C. Polymer clay does not burn at this temperature. It might turn a wee bit darker or amber colored, especially when baked for a long time. But in your project, the Premo clay is already gold colored. It’s also not on the surface. It’s well-protected on the inside of the project and therefore wouldn’t have direct exposure to the heating element.

In addition, a purse will need to be very durable. The Kato is a good choice, as it’s a very hard clay after baking. For its full durability, it should be baked as hot as your project can tolerate. In this case, I think 300°F/150°C will be fine.

Please make sure your baking setup is reliable and you’re using an oven thermometer, of course. 🙂 I also always recommend that you cover your project for additional protection from the radiant heat of the oven’s element.

Happy purse-making!